The present invention relates to a water-sealed camera, and more particularly to a water-sealed camera arranged in such a manner that a portion relatively movable to a camera body, such as a receiving lens barrel capable of forward and reverse movement, is further sealed against water.
Recently, various Rinds of cameras arranged to be sealed against water have been proposed. These water-sealed cameras remain unaffected when they become wet in the rain or may be used in the sea or rivers.
Cameras have increasingly been fitted with a bifocal, multifocal, or zoom lens, i.e, a portion movable relative to a camera body. The bifocal or zoom lens, hereinafter referred to as the "zoom lens", is arranged in such a manner that the receiving lens barrel is forwardly and reversely moved relative to the camera body. However, it has been difficult to make watertight a gap between the annular receiving lens barrel arranged to be moved and the camera body, or the fixed external cylinder secured on the camera body. If a so-called "O"-ring is employed to make the gap watertight, for instance, a problem still exists in that sliding resistance considerably increases when the receiving lens barrel moves.
Further, during wide angle photography, the receiving lens barrel is located at a position where it is completely retracted within the camera body or the fixed external cylinder. On the other hand, the receiving lens barrel is caused to be completely projected during a telephotography state. In other words, the internal volume of the camera increases when a wide angle photography state is switched to a telephotography state, whereas it reversely decreases when a telephotography state is switched to a wide angle photography state. For this reason, if the gap between the receiving lens barrel and the camera body is made watertight, that is, if zooming operation is carried out to implement the telephotography state while the internal and external pressures are in equilibrium (for example, when the receiving lens barrel has been located in the wide angle photography state), the internal pressure decreases as the internal volume of the camera increases during projection of receiving lens barrel. Consequently, great force becomes required to forwardly project the taking lens barrel. Further, since the internal pressure decreases as the receiving lens barrel is move forward, there is a risk of water penetrating into the camera during forward displacement of the receiving lens barrel.
On the other hand, if the receiving lens barrel is retracted while the internal and external pressures are in equilibrium during a telephotography state, the internal pressure rises as the internal volume decreases. Great force is therefore also required to retract the receiving lens barrel.
The above-described problems occur in a macro lens arranged in a manner such that movement of the lens barrel along the optical axis tends to become greater.